For some time it has been known that a magnetic field can be produced adjacent a permeable rotating shaft, and changes in that magnetic field can be detected by some means disposed adjacent the shaft. Thus when the shaft is loaded to provide output power to any suitable load, the shaft is stressed as a torque is developed at a certain speed of the shaft. This causes compression and tension in various portions of the shaft, which change the shaft permeability and thus vary the magnetic flux pattern. See, for example, the background explanation set out in U.S. Pat. No. 2,912,642 -- Dahle. Different methods and structures were then developed to detect the changes in the resultant magnetic field to provide some measure of the torsional stresses in the rotating shaft. A further exposition of the early development is shown in U.S. Pat. No. 3,011,340 -- Dahle. Even with these early teachings of the phenomenon itself and some devices for measuring changes in the magnetic field, there is still not an economical transducer assembly for use with a rotating shaft to provide both torque and output speed signals.
It is therefore a primary consideration of the present invention to provide a compact, economical transducer structure useful to indicate either torque or shaft output speed, or both, of a rotatable shaft.
A related object of the invention is to provide a signal processor circuit useful with such a transducer to provide the torque and/or shaft speed (rpm) signals.
Another important object of the invention is to provide such a signal processor circuit which indicates the sense of the torque and/or speed signals provided.
Yet another object of the invention is to provide such a signal processor circuit which also produces an indication of the horsepower developed by the shaft.
Another important object of the invention is to provide such a system in which the transducer is of rugged construction, suitable for use in a severe environment such as that experienced in the automotive industry where extremes of temperature, vibration and dirt are encountered.